The present invention generally relates to a continuous polymerization and condensation process for converting a radically-polymerizable monomer with a condensation reactive functionality and a modifying agent with a functional group capable of reacting with the condensation reactive functionality into a polymeric product. The invention also relates to polymeric products produced by the process and to various products that contain the polymeric product.
Processes for preparing polymers are well known in the art. However, many of the processes used to date to produce polymers for industrial use suffer from significant limitations, including high cost, significant gelation problems when a high degree of functionality is present, and an inability to produce polymers having particular desirable characteristics.
U.S. Pat. No. 4,414,370 discloses a continuous bulk polymerization process for polymerizing vinylic monomers to prepare low molecular weight polymers employing thermal initiation at reaction temperatures from 235xc2x0 C. to 310xc2x0 C. and residence times of at least 2 minutes in a continuous stirred reactor zone. The vinylic monomers of the disclosed process include styrenic monomers such as styrene and xcex1-methylstyrene; acrylic monomers such as acrylic acid, methacrylic acid, acrylates, methacrylates; and other non-acrylic ethylenic monomers such as vinyl acetate.
U.S. Pat. No. 4,529,787 discloses a continuous bulk polymerization process including an initiator for preparing low molecular weight, uniform polymers from vinylic monomers at short residence times and moderate reaction temperatures to provide high yields of a product suitable for high solids applications. The disclosed vinyl monomers include styrenic monomers such as styrene and xcex1-methylstyrene; acrylic monomers such as acrylic acid, methacrylic acid, acrylates, methacrylates, and functional acrylic monomers; and non-acrylic ethylenic monomers such as maleic anhydride and vinyl pyrrolidinone.
U.S. Pat. No. 4,546,160 discloses a continuous bulk polymerization process for polymerizing acrylic monomers to prepare low molecular weight, uniform, polymers for use in high solids applications which uses a minor amount of initiator at short residence times and moderate temperatures.
Various attempts have been made to improve the physical properties of polymers by replacing one type of polymerizable monomer for another, or by reacting a polymer with a group that will be incorporated into the polymeric structure. For example, U.S. Pat. No. 5,130,369 discloses a process for preparing functionalized polymeric compositions.
U.S. Pat. No. 5,521,267 discloses a process for preparing polymers from ethylenically unsaturated compounds containing acid groups with further ethylenically unsaturated compounds and monohydroxy compounds.
There has been no disclosure as to how a polymerization and condensation process can be performed in a continuous manner with high conversion such that gelation is avoided in such processes where cross-linking is possible due to multiple functionality on one or more of the components.
The polymer industry has long known that continuous polymerization processes are useful for obtaining large quantities of polymeric product. Furthermore, optimized continuous processes provide economic advantages over batch polymerization processes and may provide more uniform polymeric products. Additionally, many radically-polymerizable monomers containing desirable modifying groups are considerably more expensive than the precursors that they are made from. Thus, while continuous processes have been disclosed for the preparation of certain polymeric products for use in high solids coatings applications, a high temperature continuous process is needed for preparing polymeric products with improved characteristics achieved through reaction conditions and incorporation of a desired modifier in the reaction zone. Furthermore, a need remains for a continuous polymerization process in which a modifying agent may be incorporated into a polymeric chain with a high degree of conversion while also allowing for the architecture of the polymeric chain to be manipulated.
It would be highly desirable to be able to produce a polymeric product using a continuous polymerization and condensation reaction wherein a modifying agent is incorporated into the polymeric chain in the reaction zone while gelation is avoided and manipulation of the architecture of the polymeric chain is allowed.
One object of the invention is to provide a continuous polymerization and condensation process including continuously charging into at least one primary reactor: at least one radically-polymerizable monomer having a radically polymerizable group and also having at least one condensation reactive functionality; and at least one modifying agent having at least one functional group capable of reacting with the condensation reactive functionality on the radically-polymerizable monomer. The process also includes maintaining an effective temperature in the primary reactor sufficient to cause polymerization of the monomer and to allow at least a portion of the condensation reactive functionality to react with the functional group of the modifying agent such that a first polymeric product is produced which incorporates at least some of the modifying agent and the polymeric product is formed substantially free of gelation.
In some preferred processes, at least two different radically-polymerizable monomers are charged into the primary reactor while in other preferred embodiments the radically-polymerizable monomer has at least two condensation reactive functionalities. In some preferred processes, the modifying agent has one functional group capable of reacting with the condensation reactive functionality while other preferred processes include modifying agents with more than one such functional group. In some preferred processes the two functional groups on a multifunctional modifying agent are similar, while in others they are different from one another. Multifunctional modifying agents may be polymeric or non-polymeric, and in various preferred processes both a monofunctional modifying agent and a multifunctional non-polymeric modifying agent are employed.
A polymeric product of the process may contain a cyclohexyl group, and in preferred processes the radically-polymerizable monomer is acrylic acid and the modifying agent is cyclohexanol. In other preferred processes, at least one vinyl aromatic monomer is continuously charged into the primary reactor while in still other preferred processes at least two different vinyl aromatic monomers are charged into the reaction zone.
In preferred processes, the condensation reactive functionality is a carboxyl, an ester, an anhydride, a hydroxy, an epoxy, an amine, a ketone, an aldehyde, or an isocyanate functionality while in other preferred processes, the functional group of the modifying agent is a carboxyl, a hydroxy, an anhydride, an amine, an epoxy, or an isocyanate group.
In various preferred processes, the temperature is maintained between about 175xc2x0 C. and about 345xc2x0 C. in the primary reactor while in other preferred processes the temperature is maintained above 300xc2x0 C. In still other preferred processes, the flow rate through the primary reactor is maintained to provide an average residence time of 60 minutes or less in the primary reactor.
In some preferred processes, one or more additional components such as a radically-polymerizable monomer substantially free of condensation reactive groups, an inert solvent, a byproduct removal agent, or an initiator are added to one or more reactors in the process while in other preferred processes a catalyst such as an esterification, transesterification, or amidation catalyst is added to one of the reactors. In still other preferred processes, the reaction zone is substantially free of an inert solvent.
In yet other preferred processes, the process further includes a secondary reactor and the process further includes charging the first polymeric product from the primary reactor into the secondary reactor and thereafter removing a second polymeric product from the secondary reactor. In some preferred processes the primary reactor is a continuous stirred tank reactor or a loop reactor while in other preferred embodiments the secondary reactor is a loop reactor, a tube reactor, an extruder reactor, or a continuous stirred tank reactor or any reactor suitable for continuous operation. In still other preferred processes, at least one of the polymeric products is continuously charged into an extruder reactor and additional modifying agent is charged into the extruder reactor to produce a polymeric product. The product can be added to a batch reactor for further modification. In still other preferred processes, the temperature in the primary and secondary reactors are different from one another, and are preferably independently controlled.
In various preferred processes, at least a portion of the modifying agent is added to the secondary reactor while in other preferred processes the modifying agent is added to two different reaction zones in the secondary reactor. In still other preferred processes, at least two different modifying agents are added to each of two different reaction zones in the secondary reactor.
In preferred processes, at least one reactor in the reaction zone includes a headspace and the process includes purging the headspace with an inert gas. In more preferred processes, a volatile material is separated from the primary reactor to produce two streams. One of the streams is relatively free of byproduct while the other stream contains unreacted starting materials. In preferred processes, the stream that is relatively free of byproduct is added to a reactor in the reaction zone.
Another object is to provide a polymerization and condensation process which includes charging into a reaction zone at least one radically-polymerizable monomer having a radically polymerizable group and also having at least one condensation reactive functionality; and at least one modifying agent having at least one functional group capable of reacting with the condensation reactive functionality on the radically-polymerizable monomer. The modifying agent is a polyamide, a polyurethane, a polyacrylate, or a polyorganosiloxane, and the process includes maintaining the temperature in the reaction zone at an effective temperature to cause polymerization of the monomer and to allow at least a portion of the condensation reactive functionality to react with the functional group of the modifying agent to produce a polymeric product.
Yet another object is to provide a continuous polymerization and condensation process including continuously charging into a primary reactor at least one radically-polymerizable monomer having a radically polymerizable group and also having at least one condensation reactive functionality, with the primary reactor being free of any modifying agent. The process also includes maintaining the temperature in the primary reactor at an effective temperature to cause polymerization of the monomer to produce a first polymeric product; charging the first polymeric product into a secondary reactor; and charging the secondary reactor with at least one modifying agent having at least one functional group capable of reacting with the condensation reactive functionality to react with the functional group of the modifying agent to produce a second polymeric product.
Still another object of the invention is a continuous polymerization and condensation process, which includes continuously charging into a reactor at least one radically-polymerizable monomer having a radically polymerizable group and also having at least one condensation reactive functionality together with at least one modifying agent. The modifying agent has at least one functional group capable of reacting with the condensation reactive functionality on the radically-polymerizable monomer. In a preferred embodiment, each modifying agent is a monohydroxy alcohol; however, each modifying agent is not a monohydroxy alcohol having the formula ROH, wherein R is a linear or branched chain alkyl radical having greater than 11 carbon atoms. Further the polymerization takes place in the absence of any monohydroxy alcohol having the formula ROH, with R being a linear or branched chain alkyl radical having greater than 11 carbon atoms. The temperature in the reactor is maintained at an effective temperature in the reactor to cause polymerization of the monomer and to allow at least a portion of the condensation reactive functionality to react with the functional group of the modifying agent to produce a polymeric product which incorporates at least some of the modifying agent.
Still another object is to provide the polymeric product prepared by any of the above processes and to provide overprint varnishes, coatings, coating modifiers and compatibilizers, dispersants, surfactants, and paints including the polymeric product.
Still further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the drawings.